In a (non-aluminum) saucepan, cook the rhubarb over medium-high heat until it starts to release some juices. Add 2 cups of sugar along with the vanilla bean, both the skin and scraped seeds, and continue to cook. When the sugar is dissolved and the mixture comes to a boil, turn the heat down to medium-low. Cook jam for about half an hour, stirring occasionally, until the all of the chunks of rhubarb have broken up and the mixture starts to thicken. At this point, taste the jam for sugar and add more if you like. To check the thickness, take a teaspoon of jam and put it on a plate in the freezer. Once it's cool, check and see if it’s the thickness you like. If not, continue to cook for several minutes and check again.

Jam will keep in the fridge for several weeks. Freeze any you’d like to keep longer. If you are canning-inclined, feel free to jar this jam as usual; it does start to turn a little bit brown over time, but the flavor remains.